No abstract available

[en] The magnetic and transport properties of La_0.5Sr_0.5CoO_3-δ film grown on a LaAlO₃ substrate by pulsed-laser deposition are studied. The properties are found to be influenced by a combined influence of the magnetic anisotropy and inhomogeneity. Magnetoresistance anisotropy is determined by the shape anisotropy and the strain-induced magnetic anisotropy due to the film-substrate lattice interaction. Indications of the temperature-driven spin-reorientation transition from an out-of-plane ordered state at low temperatures to an in-plane ordered state at high temperatures as a result of competition between the mentioned anisotropy sources are found

[en] Magnetic susceptibility of the weak itinerant-electron ferromagnet MnSi (T_c approx = 30 K) in the paramagnetic state was studied under hydrostatic pressure up to 2 kbar in the temperature range 78-300 K. Analysis of the experimental data in the framework of the Stoner model modified by taking into account the spin fluctuations made it possible to estimate the volume derivative for the parameter of the effective electron-electron interaction, d ln J/ d ln V = - 1.4 ± 0.1, and the density of electronic states at the Fermi level, d ln N(E_f)/d ln V = 2 ± 0.5. The noticeable volume dependence of J obtained suggest an essential role of electron correlations in magnetism of the compound

[en] The hopping conductivity of single-crystal La₂ CuO_4+δ with excess oxygen is studied.It is found that the transition from the variable-range hopping conductivity (with the temperature dependence of resistance R ∝ exp (T₀/T)^1/4 to a simple activation one (R propor to exp (Δ/kT)) occurs as the temperature is lowered below 20 K.The transition is followed by essential changes of magnetoresistance and voltage-current characteristics behavior.It is shown that such behavior of the hopping conductivity below 20 K may be attributed to the superconducting inclusions occurred in the insulating sample because of the phase separation. The observed peculiarities of the conducting properties agree well with the known effects of competition between electron localization and superconductivity in inhomogeneous systems

[en] The experimental data on fluctuation diamagnetism of YBa₂Cu₃O_7-δ and Bi₂Sr₂CaCu₂O_8+δ compounds at T>T_c obtained both by the authors and other researchers are briefly reviewed. Studies into this property make it possible to obtain reliable quantitative data on anisotropy and dimensionality which are essential for developing nontraditional theories of high-T_c superconductivity most of which includes lower-dimensional elements. Comparison of the values of fluctuation effects for T>T_c and T< T_c could provide a direct information on the character of pairing. (O.K.)

[en] The pressure dependence of the enhanced spin susceptibility of some transition d-metals, alloys and compounds is reviewed. The results unambiguously confirm the predominant role of the short-range correlations in the electron-electron interactions in these systems

[en] A method based on the analysis of fluctuation contributions to thermal capacity and magnetic susceptibility is proposed to estimate the upper critical derivatives with respect to temperature for high-T_c superconductors. The fluctuaton contribution to magnetic susceptibility of YBa₂Cu₃O₇ is measured, and the above derivatives for this superconductor are evaluated

[en] The unusual non-linear effects in hopping conduction of single-crystal La₂ CuO_4+δ with excess oxygen has been observed. The resistance is measured as a function of the applied voltage U (voltage controlled regime) in the temperatures range 5 K ≤ T ≤ 300 K and voltage range 10^-3 - 25 V. The results obtained demonstrate that in some cases the measured transport properties of cuprate oxides cannot be attributed to the intrinsic bulk properties

No abstract available

[en] First-principles calculations of the electronic structure and a number of thermodynamical characteristics are performed for the ternary superconducting systems RRh_4B_4 (R = Y, Lu) in the normal state. The analysis of electronic states and their interactions responsible for superconducting and magnetic properties of the investigated systems is carried out. It is found that in YRh_4B_4 and LuRh_4B_4 compounds the Fermi level is situated in close proximity to a peak in the density of electronic states, and about 1 eV above of the pseudo-gap in the electronic spectrum. The existence of a number of groups of quasi-degenerate electronic states with a small effective mass near the Fermi level is revealed. These states can be the origin of a substantial conduction electrons diamagnetic contribution to the magnetic susceptibility, and can provide strong temperature dependences of the susceptibility in the rhodium borides.